Electric-lighting device.



C. E. CAMPBELL.

ELECTRIC LIGHTING DEVICE.

APPLICATION FILED APR.2. I914.

Patented Nov. 30, 1915 M; 2/2 1 H /z2 -21! If 2,1 M

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CHARLES E. CAMPBELL, 0F LYNN, MASSACHUSETTS, ASSIGNOR 0F ONE-HALF TOFREDERICK R. CAMPBELL, OF LYNN, MASSACHUSETTS.

ELECTRIC-LIGHTING DEVICE.

Specification of Letters Patent.

Patented Nov. 30, 1915.

Application filed April 2, 1914. Serial No. 829,001.

To all whom it may concern:

Be it known that I, CHARLEs E.- CAMP- BELL, a citizen of the UnitedStates, residing at Lynn, in the county of Essex and State ofMassachusetts, have invented certain new and useful Improvements inElectric-Light ing Devices, of which the following is a specification.

My invention relates to improvements in electric lighting devices andthe object of my improvement is to provide means for supplying thelighting current to a filament inclosed in a hermetically sealed glasschamber or bulb without the use of leading in wires or conductors thatpass through the glass wall and thereby obtain certain susuch leading inwires or conductors are used.

In the accompanying drawing, Figure 1 is a side elevation of my improvedlighting device. Fig. 2 is a plan view of the same. Fig. 3 is asectional view on the line 01-00 of Fig. 2, the core being shownin sideelevation.

My improved electric lighting device comprises a filament 10 of tungstenor other material suitable for incandescent lighting inclosed in a bulb11 of special construction and with which there is incorporated in aspecial manner tobe described a transformer 12. The lower part of thebulb 11 is of any form suitable for housing the filament 10. As shownthe filament 10 is short and straight and extends laterally across thecentral part of the said lower portion and the tip 13 is just below thesame. The upper portion of the bulb 11 is relatively extended for anappreciable distance, suitably to have the transformer 12 incorporatedtherewith and comprises a cylindrical peripheral wall 11 and an axiallyextending recess 15 having a cylindrical wall 16 concentric with theouter wall 14. Between the outer wall 1% and the inner wall 16 there isan annular space 17, within the bulb walls and constituting an extensionof the bulb space in which the filament 10 is housed. The secondarywinding 18 of the transformer 12 is housed in the annular space 17 andsubstantially fills the same. The conductors 19 extend. directly fromthe secondary winding 18 to the filament 10, and they may be providedwith a brace or bridge 20, preferably of glass, at some pointintermediate the ends whereby they are crossconnected mechanically andpositively positioned relatively one to the other. The core 21 and theprimary winding '22 are positioned in any suitable manner relatively tothe secondary winding 18 to operate inductively therewith. Obiously, inorder to do this, one leg of'the core; shown as '23, must be positionedaxially with reference to the secondary winding 18, and the primarywinding 22 is conveniently positioned concentric with the said leg 23and with the secondary winding 18.

I find it convenient to mount the primary winding 22 directly on the leg23. as shown.- The primary winding 22. mounted on the leg 23, asmentioned. substantially fills the recess 15. The return portion of themag netic circuit'of the core 21 may be formed in plurality of yokes 25.The core as shown is 1 made up of four similar units 26. each of whichis built up of U-shaped laminations of ordinary form to provide a squarecrosssection for the arms 2-1. The four individual arms 2 1 on one sideof each of the units 26 are combined to build up the axial leg 23, andwhich has a square cross-section.

It is understood that the constructive details may be varied in variousways from those shown and described. It will be noted that the currentsupplied to the filament is delivered directly from the secondary of thetransformer, and the current is accordingly delivered thereto byinduction through the walls of the bulb, and without leading in wirespenetrating the glass walls of the bulb.

Vhile there are advantages in the use of .the construction describedwith filaments of would be made of platinum, and correspond inglyexpensive. Furthermore, with low voltage, as mentioned, there would beexcessive drop in voltage and also loSs of energy due to the length ofthe leading in wires and the means of delivering the current thereto bysuch methods as are ordinarily used for this purpose. These diflicultiesare obviated by my invention. As an example, I have successfully used aprimary winding for 110 volts 'and a filament for one volt. The air maybe exhausted from the bulb 11 so that the filament 10 will be operatedin a vacuum or the said bulb may be supplied with a special arrangementof gases. \Vith such a special. arrangement of gases a filament such asshown, that is short and of relatively large diameter, and ofcorrespondingly large current capacity, gives the best efficiency, as ifthe filament is of small diameter and great length the percentage ofloss by the heat being conducted through the gas, which usually amountsto three quarters of an atmosphere, is appreciably greater than if thefilament is of only a fraction of the length and correspondinglyheavier. In such cases the voltage drop due to leads and contacts underordinary methods of construction is liable to be excessive and theseconditions are avoided by my invention.

I claim as my invention 2- 1. In combination, a hermetically sealedglass bulb, a secondary winding and a filament housed in the said bulb,a primary winding, and a core having a plurality of legs. said bulbhaving a recess extending inwardly along the axis of the said secondarywinding, the said primary winding and one leg of the said core beinghoused in the said recess, and the other legs of the said core beingdistributed over the outer side of the said secondary and extendingalongthe said bulb in parallel relation to the said first leg.

2. In combination a hermetically sealed glass bulb, a secondary .windingand a filament housed in the said bulb, a primary winding, and a corehaving an inner and an outer leg, the said bulb having a recessextending inwardly along the axis of the secondary winding, the saidprimary and the said inner leg being housed in the said recess, and thesaid outer leg of the said core being positioned on the outer side ofthe said secondary and extending along the said bulb in parallelrelation to the said inner leg.

CHARLES E. TAMPBELL.

Witnesses:

JENNIE SCHwAnTz, MAE HAGAN.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

' Washington, D. 0.

